The invention relates to a laundry mangle comprising at least one mangle roller, which is held in a service position by means of at least one supporting arm in a heatable trough. The mangle roller and the trough assume a moveable position relative to each other having at least one adjusting means that defines an inlet and outlet for the passage of laundry articles.
A conventional laundry mangle described in PCT/WO 85/03313 includes several mangle rollers arranged successively in series. Due to the adjustability of the respective mangle roller to the assigned trough, an approximately parallel, preferably coaxial positioning of the longitudinal axes of the roller and semi-rotary cylinder can be obtained, a feature that should guarantee a frictionless operation of the mangle. Furthermore, it is possible to swing the mangle roller completely into or out of the trough, in order to have unimpeded access to the trough, for example, for the purpose of removing the laundry articles that have become either caught, or for cleaning and/or for ventilation.
To this end, the ends of the bearing axle of the respective mangle roller can be rotated using a pair of supporting arms, which can be swung up and down by means a working cylinder around a stationary bearing point. To provide a frictionless operation, the bearing, which can adjusted within a narrow range, in the form of a bearing point, is then set in such a manner that a coaxial service position between mangle roller and assigned trough is achieved as far as possible; a position that is then fixed in the effective service position.
The friction generated in this service position that is set once, between the mangle roller and the surface of the trough and that should have as low a value as possible does not remain, however, uniform and constant during service. First, due to its torque the driven mangle roller has the tendency to move in the direction of the trough on the inlet side of the mangle, a state that reduces on the inlet side the distance between mangle roller and trough, thus resulting in raised frictional values at this point. Secondly, the friction on the trough surface changes in an irregular and unpredictable manner, due to for example, nonuniform heating, or, during the introduction of laundry articles having different sizes, thicknesses and also frictional values. As these articles are dragged along by the roller surface friction results along the trough surface
This frictional force thus generated leads to a nonuniform and raised ironing pressure especially in the inlet sided region of the mangle. At the same time the mangle performance drops, since the ironing pressure on the laundry outlet side of the mangle drops due to the corresponding increase in distance from the trough, thereby reducing the thermal transfer required. In the inlet sided region, the ironing pressure increases only insignificantly as the pressure increases. The high pressure on the inlet side results in an undesired high wear not only on the laundry articles but also on the roller lining applied on the surface of the mangle roller.
A mangle of the aforementioned type is described in DD-PS 24 331, where the mangle roller and the trough assume by means of the adjusting means a moveable position relative to each other while the mangle is operating. On both sides the mangle roller is mounted on a supporting arm, by means of which it can be swung out; and simultaneously a drive wheel for the mangle roller is mounted on the swivel pin. Mangle roller and drive wheel are connected by the meshing of a gear wheel. To eliminate the resulting tooth pressure, which leads to a nonuniform ironing or pressing pressure within the trough, the known rotary mangle provides that between the gearwheel of the roller axle that exhibits the same or approximately the same diameter, and the actual drive wheel on the supporting arm there is an intermediate wheel, which can also be swung out. Furthermore, a spring energy store engaging at the support arm is provided as the adjusting means. The addressed deleterious tooth pressure is, in fact, eliminated with this known mangle. Yet at the same time forces are generated that push the mangle roller on the inlet side against the trough and move away from said trough on the outlet side. The result is an increase in the frictional force and thus a nonuniform ironing pressure that is excessive on the inlet side with the aforementioned drawbacks.
Another mangle of this type is described in DE-OS 1 813 594 wherein the mangle roller is suspended rotatably from a supporting arm, which forms a rocking arm and which is attached in such a manner to a mangle housing that it slopes upward from the roller axle to the housing suspension, thus resulting in an angle ranging from 0.degree. to 90.degree. between the rocking arm and a horizontal line extended through the center point of the roller, when seen in the direction of rotation. The larger the angle is chosen, the greater is also the contact force of the roller on the trough, and the greater is the frictional force between the mangle roller and the trough. Not to exceed at this stage a deleterious maximum frictional value as the strength of the laundry articles increases, the trough can be swivelled flexibly by means of adjusting means as a spring energy store. With this known laundry mangle the resulting frictional force can be compensated for only partially and in particular the ironing pressure cannot be set either constantly or increasingly in the direction of the outlet side.
In another type of conventional laundry mangle which is described in DE-AS 1 211 122 the mangle roller is pivot-mounted on supporting arms by means of one pair and enveloped in the swung-in state stationarily by an ironing trough, which is designed as a half shell and whose free ends are driven by means of a mechanical device or with a heating medium in such a manner that they move toward each other during service in order to increase the ironing pressure, thus reducing on the inlet and outlet side the distance between the mangle roller and trough. In addition to decrease the pressing pressure the mangle roller can be simultaneously lifted by means of the two supporting arms. With this known mangle roller the ironing pressure for the laundry articles can be increased on the inlet and outlet side, so that at these points altogether high frictional values with the drawbacks described above are generated. contrast, the frictional values drop in the center of the trough and the ironing pressure decreases dramatically, so that altogether the mangle output of this known mangle is low.
Thus, it can be seen from the prior art, that there is a need to provide a laundry mangle, where the described drawbacks are avoided.